The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. For example, lactate, cholesterol and bilirubin should be monitored in certain individuals. In particular, determining glucose in body fluids is important to diabetic individuals who must frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered. In one type of blood glucose testing system, test sensors are used to test a fluid such as a sample of blood.
A test sensor contains biosensing or reagent material that will react with the analyte of interest, such as blood glucose. The testing end of the test sensor is adapted to be placed into the fluid being tested, for example, blood that has accumulated on a person's finger after the finger has been pricked. The fluid is drawn into a capillary channel that extends in the test sensor from the testing end to the reagent material by capillary action so that a sufficient amount of fluid to be tested is drawn into the test sensor. In some test sensors, the fluid then chemically reacts with the reagent material in the test sensor resulting in an electrical signal indicative of the glucose level in the fluid being tested.
One problem with current test sensors is that the reagents may contain components that interfere with sensor stability. In particular, some components, such as polyethylene oxide (“PEO”), may be incompatible with other components, such as the enzyme and the electron transfer mediator, which are important for test sensors. Test sensors having reagents that are formulated with components that are, for example, incompatible with the enzyme and the electron transfer mediator may exhibit poor test sensor stability over time. This instability is especially apparent when the total assay time is less than about 35 seconds. Thus, it would be desirable to have a test sensor reagent having components that improve test sensor stability.